Large gate valves are commonly used in a wide range of applications, including mining, manufacturing, refining, sewer and water, and many others. In many of these applications, such as the use of large gate valves in the transportation of water, the valves can remain in use for many years, and even decades, with relatively little significant maintenance or service. However, many other large gate valves are used in extremely challenging environments where the interior surfaces of the valve components are exposed to abrasive or corrosive materials that can rapidly degrade all but the most durable of materials. For example, carrying of mining slurries with significant amounts of rock and sand can wear away interior valve components prematurely. Similarly, tar sands, such as those mined in western Canada to make alternative fuels, are processed at elevated temperatures and with very high solids contents that readily degrade the interior of valves as they pass through.
In order to promote longer service life of valves, especially large gate valves that operate in extreme conditions, it is possible to create replaceable surfaces that line portions of the inside of the valves. These replaceable surfaces can be made of much harder materials than the other valve components—in part because they require less elaborate machining than other parts, and also because they can use higher priced metals without requiring use of expensive materials throughout the valve. In addition, the removable nature of the surfaces allows them to be replaced without replacing or rebuilding the entire valve.
Unfortunately, one challenge of existing gate valve designs, even those that use replaceable wear resistant surfaces, is that materials used to make these wear resistant surfaces are often so hard that they can be difficult to machine to fine tolerances. Of particular difficulty in machining are curved surfaces, such as the outer diameter of wear rings that are designed to tightly fit into a valve body. However, in order to fit properly within the valve body the wear rings must have relatively precise external shape and dimensions. It is possible to machine such dimensions, but the time and expense of satisfactory machining of such surfaces can be exceedingly high due to the hard nature of the materials necessary to have suitable wear properties. In addition, the extremely hard alloys used for such wear surfaces are also often quite brittle, and can crack under the machining stresses. Therefore, a need exists for improved wear surfaces for use within valves, in particular improved wear rings that can be formed without excessive machining